Specialized silica, rubber composition containing specialized silica and products with component thereof

ABSTRACT

The invention relates to allyl functionalized precipitated silica, rubber compositions containing such silica, particularly sulfur cured rubber compositions, and articles of manufacture having a component thereof such as, for example tires. The invention particularly relates to synthetic amorphous silica, particularly a precipitated silica, treated with an allyl silane, particularly to a precipitated silica containing allyl functional groups.

The Applicants hereby claim the benefit of prior U.S. ProvisionalApplication Ser. No. 61/223,434, filed on Jul. 7, 2009.

FIELD OF THE INVENTION

The invention relates to allyl functionalized precipitated silica,rubber compositions containing such silica, particularly sulfur curedrubber compositions, and articles of manufacture having a componentthereof such as, for example tires. The invention particularly relatesto synthetic amorphous silica, particularly a precipitated silica,treated with an allyl silane, particularly to a precipitated silicacontaining allyl functional groups.

BACKGROUND OF THE INVENTION

Rubber compositions are often reinforced with reinforcing fillers suchas at least one of rubber reinforcing carbon black and syntheticamorphous silica (e.g. precipitated silica).

Various products contain at least one component comprised of such rubbercompositions such as, for example, tires.

In order to enhance rubber reinforcing effects of precipitated silica, acoupling agent is typically used in combination with the precipitatedsilica.

Such coupling agent typically contains a moiety (e.g. alkoxysilanegroup) reactive with hydroxyl groups (e.g. silanol groups) on theprecipitated silica and another different moiety (e.g. polysulfide as asulfur contributing moiety) interactive with elastomers containingcarbon-to-carbon double bonds (e.g. diene-based elastomers).

A typical disadvantage of such polysulfide moiety of the silica couplingagent is its sulfur contribution at an elevated temperature of theuncured rubber composition, such as for example during physical mixingof the uncured rubber composition, which interacts with carbon-to-carbondouble bonds of an elastomer in the rubber composition to promote asignificantly increased viscosity of the rubber composition which leadsto increased rubber processing difficulties, or challenges. Suchphenomenon is well known to those having skill in such art.

For this invention, a rubber reinforcing precipitated silica is usedwhich may usually be characterized by having typical properties for asynthetic precipitated silica used for reinforcing rubber compositionssuch as a BET nitrogen surface area in a range of from 120 to 300 m²/g;a CTAB surface area in a range of from 100 to 300 m²/g, with a ratio ofthe BET/CTAB surface areas in a range of from 0.8 to 1.3.

The BET nitrogen surface may be determined according to ASTM D1993, orequivalent, and the CTAB surface area according to DIN53535.

A significance of providing the precipitated silica with the requiredBET/CTAB ratio for rubber reinforcement purposes is exemplified inpatent literature as a value in a range of, for example, from 0.8 to 1.3with a BET surface area of, for example 120 to 300 m²/g and a CTABsurface of, for example, 100 to 300 m²/g. For example, see U.S. PatentApplication Serial No. 2008/0293871, U.S. Pat. No. 6,013,234 and EPPatent Publication No. 0901986.

The DBP absorption value, or number, may be determined according to DIN53601 or equivalent.

In one embodiment, such precipitated silica might be typlified, forexample, by mercury porosimetric parameters of, for example and asmeasured by a CARLO-ERBA Porosimeter 2000 or equivalent as a surfacearea in a range of from 100 to 240 m²/g, and pore size distributionmaximum in a range of from 20 to 75 nm (nanometers).

For this invention, it has been discovered that an allyl functionalizedrubber reinforcing precipitated silica may be used as silicareinforcement for a rubber composition. Such allyl functionalized silicadoes not contain a polysulfidic moiety so that sulfur is not availableto prematurely interact with the elastomer(s) in the rubber composition.Where the allyl functionalized precipitated silica is formed, forexample, by treatment of a precipitated silica with anallyltrialkoxysilane or allylhalosilane, it is envisioned that analkoxysilane moiety of the allylalkoxysilane or halogen moiety of theallylhalosilane reacts, for example, with hydroxyl groups (e.g. silanolgroups) and/or hydrogen groups on the precipitated silica. The treatedsilica thereby contains allyl hydrocarbon groups which can beinteractive with, and thereby couple the silica with diene-basedelastomer (elastomer formed by polymerization of monomers containingdiene hydrocarbons) in the presence of sulfur curative during thesubsequent vulcanization of the rubber composition.

It is further envisioned that, if desired, a beneficially relativelyhigh temperature mixing of the allyl functionalized silica with theelastomer(s) can occur without an attendant sulfur-promoted viscosityincrease of the rubber mixture prior to addition of the sulfur andsulfur cure accelerators to the rubber mixture. It is envisioned thatsuch higher temperature mixing of the rubber composition provides anopportunity for more efficient mixing of the rubber composition for ashorter mixing time.

Further, it is envisioned that the presence of allyl functional groupson the silica (e.g. precipitated silica) surface provide a degree ofhydrophobicity to the silica surface to thereby enhance, or improve, itsdispersion within the rubber mixture with a consequent enhancement, orimprovement, in its reinforcement of the rubber composition.

Representative examples of various allyl silanes for preparation ofallyl functionalized silica are, for example, allyltriethoxysilane,allyltrimethoxysilane, allyldimethylchlorosilane, allyltrichlorosilane,allylmethyldichlorosilane, diallylchloromethylsilane,diallyldichlorosilane and triallylchlorosilane.

In the description of this invention, the term “phr” relates to parts byweight for a material or ingredient per 100 parts by weightelastomer(s)”. The terms “rubber” and “elastomer” are usedinterchangeably unless otherwise indicated. The terms “cure” and“vulcanize” are used interchangeably unless otherwise indicated.

SUMMARY AND PRACTICE OF THE INVENTION

In accordance with this invention an allyl silane treated (modified)synthetic amorphous silica (precipitated silica) is provided which maybe referred to herein as an allyl functionalized precipitated silica.

Such allyl functional precipitated silica is provided by treatingsynthetic amorphous silica (precipitated silica) with at least one allylsilane.

For this invention, an allyl functional precipitated silica is providedwhich is comprised of a precipitated silica containing at least oneallyl group substituent;

wherein said precipitated silica has:

(A) a BET nitrogen surface area in a range of from 120 to 300 m²/g,

(B) a CTAB surface area in a range of from 100 to 300 m²/g, with

(C) a ratio of said BET/CTAB surface areas in a range of from 0.8 to1.3;

wherein said allyl functionalized precipitated silica is represented bya general formula (I):

where Z represents the precipitated silica; R² and R³ are the same ordifferent radicals comprised of an alkyl group containing from 1 to 4carbon atoms, a cycloalkyl group, a phenyl group, and alkene groupcontaining from 3 to 18 carbon atoms or cycloalkene radical having from5 to 8 carbon atoms; and R¹ is an allyl hydrogen containing hydrocarbonradical. Desirably, said allyl containing hydrocarbon radical iscomprised of at least one of:

—CH₂—CH═CH₂, (allyl hydrocarbon radical)

—CH₂—CH═CH—CH₃, (2-butene radical)

—CH₂—CH═C—(CH₃)₂ and (dimethallyl hydrocarbon radical)

—CH₂—C(CH₃)═CH—CH₃ (2-methyl-2-butene radical)

where a is an integer in a range of from 0 to 2, b is an integer in arange of from 0 to 2 and c is an integer in a range of from 1 to 3.

In one embodiment, the said precipitated silica might have, for example,mercury porosimetric parameters of:

(A) surface area in a range of from 100 to 240 m2/g, and

(B) pore size distribution maximum in a range of from 20 to 75 nm.

In practice, said allyl functionalized precipitated silica may be in aform of aggregates of coalesced primary particles thereof with anaverage aggregate size, for example, in a range of from about 0.8 toabout 1.2 microns.

In further accordance with this invention, said allyl silane has ageneral formula (II):

where R² and R³ are the same or different and comprised of an alkoxygroup containing from 1 to 8 carbon atoms, a cycloalkoxy groupcontaining from 5 to 8 carbon atoms, an alkyl group containing from 1 to4 carbon atoms, a cyclohexyl group, a phenyl group, an alkene containingfrom 3 to 18 carbon atoms, or a cycloalkene containing 5 to 8 carbonatoms;

where X is a chlorine, a hydroxy, or a hydrogen;

where R¹ is an allyl hydrogen containing hydrocarbon radical. Desirablysaid allyl hydrogen containing hydrocarbon radical is comprised of atleast one of:

—CH₂—CH═CH₂, (allyl hydrocarbon radical)

—CH₂—CH═CH—CH₃, (2-butene radical)

—CH₂—CH═C—(CH₃)₂ and (dimethylallyl hydrocarbon radical)

—CH₂—C(CH₃)═CH—CH₃ (2-methyl-2-butene radical)

where a is an integer with a range of from 0 to 3, b is an integer in arange of from 0 to 3, c is an integer in a range of from 1 to 3, and dis an integer in a range of from 0 to 3 and the sum of a, b, c and d is4;

wherein at least one of X, R² and R³ is present;

wherein if d=0, at least one of R² and R³ is an alkoxy group.

It is envisioned that, for the allyl functionalized precipitated silica,R² and R³ of said allyl silane are the same or different and may beselected from at least one of:

(A) alkoxy group comprised of ethoxy or methoxy groups,

(B) cycloalkoxy group,

(C) alkyl group comprised of methyl, ethyl or propyl groups,

(D) cycloalkyl group,

(E) phenyl group, and

(F) allyl hydrogen-containing alkene group. Such alkene group isdesirably comprised of allyl, 2-butene dimethylallyl or2-methyl-2-butane radical.

Representative examples of said allyl functionalized silane forfunctionalizing the precipitated silica are, for example,allylalkoxysilanes comprised of at least one of allyltriethoxysilane,allyltrimethoxysilane, and allylhalosilanes comprised of at least one ofallyldimethylchlorosilane, allyltrichlorosilane,allylmethyldichlorosilane, diallylchloromethylsilane, anddiallyldichlorosilane. A desirable allyl functionalized silane isallyltrichlorosilane.

In further accordance with this invention, a rubber composition isprovided which contains reinforcing filler comprised of said allylfunctionalized precipitated silica and which may further contain atleast one of rubber reinforcing carbon black and an additionalprecipitated silica which does not contain allyl functionalization. Suchrubber composition may further contain at least one silica couplingagent to aid in coupling said precipitated silica(s) to elastomerscontained in said rubber composition. In practice, said coupling agenthas a moiety reactive with hydroxyl groups on said silica (e.g. silanolgroups) and another different moiety interactive with elastomerscontained in said rubber composition.

For example, a rubber composition is provided which is comprised of,based upon parts by weight per 100 parts by weight rubber (phr):

(A) 100 phr of at least one conjugated diene based elastomer;

(B) about 10 to about 120, alternately about 40 to about 100, phr ofreinforcing filler wherein said reinforcing filler is comprised of:

-   -   (1) about 40 to about 100, alternately about 50 to about 80, phr        of allyl functionalized precipitated silica (allyl silane        treated precipitated silica);    -   (2) zero to about 60, alternately about 3 to about 30, phr of        rubber reinforcing carbon black, and    -   (3) optionally up to about 70 phr of precipitated silica (other        than the allyl functionalized precipitated silica).

While various methods for producing an allyl silane functionalizedprecipitated silica during the manufacture of the precipitated silicamay be contemplated, one method envisioned relates to the preparation ofprecipitated silica for rubber reinforcement purposes based upon methodsdescribed in U.S. Pat. No. 5,723,529 which may comprise:

(A) reacting at least two inorganic materials, in the presence of water,with a strong base to form a aqueous solution of a product thereof;

wherein said inorganic materials are comprised of, based on 100 parts byweight thereof,

-   -   (1) from 60 to 99.9 parts silicon dioxide, and    -   (2) from 0.1 to 40 parts of at least one additional inorganic        material capable of forming said aqueous solution, said        inorganic material being selected from at least one of:        -   (a) oxides of aluminum, iron, magnesium, boron, titanium,            zirconium, zinc, vanadium and niobium,        -   (b) salts of aluminum, iron, magnesium, boron, titanium,            zirconium, zinc, vanadium and niobium as phosphates,            sulfates and halogenides thereof, and        -   (c) natural and synthetic aluminum silicates;

(B) treating said aqueous solution by the addition of a mineral acid toreact with the said product and form a reaction product thereof and toreduce the pH of the solution to thereby produce precipitated particlesof the reaction product as a precipitate;

(C) optionally interrupting the said acid addition of step (B) to saidaqueous solution to allow the said precipitate to age for a period oftime before resuming the addition of acid, followed by adding additionalacid until a desired pH is reached to complete the said reaction andprecipitation of the reaction product;

(D) optionally, after said acid addition of step (B) and/or step (C) ifused, is completed, allowing the precipitate to age for a period oftime;

(E) filtering and washing the precipitate with water and drying theprecipitate to recover particles in a form of an aggregate thereof,

(F) addition of at least one electrolyte having an anion in any of steps(B), (C) and (D) selected from at least one of carbonate, silicate,aluminate, borate, alumino-silicate, phosphate, sulfate, halogenide,titanate and zirconate and cation selected from at least one of lithium,sodium, potassium, magnesium and/or calcium;

(G) treating the said precipitate with at least one ionic and/ornon-ionic surfactant, and

(F) addition of at least one of said (hereinbefore described) allylsilanes in or after any of steps (C), (B), (D) and (E). Desirably,therefore, said allyl silane is comprised of at least one of:

CH₂—CH═CH₂, (allyl hydrocarbon)

CH₂—CH═CH—CH₃, (2-butene)

CH₂—CH═C—(CH₃)₂ and (dimethylallyl hydrocarbon)

CH₂—C(CH₃)═CH—CH₃ (2-methyl-2-butene)

In practice, said allyl functionalized precipitated silica may be formedby pre-treating the precipitated silica with said allyl silane prior toits addition to the rubber composition or may be treated in situ withinthe rubber composition by addition of said precipitated silica and saidallyl silane individually to the rubber composition.

In further accordance with this invention, an article of manufacture,such as for example a tire, is provided having at least one componentcomprised of said rubber composition. Such tire component may be, forexample, at least one of a tire sidewall, tire sidewall insert, tiresidewall apex, ply coat, wire coat, and tread.

From a historical perspective, according to U.S. Pat. Nos. 5,708,069,7,550,610 and 5,789,514, silica gels may be derived, for example, byhydrophobating a silica hydrogel with, for example, anorganomercaptosilane and alkyl silane and drying the product. Theresulting hydrophobated silica gel may be blended with natural rubberand/or synthetic rubber.

A general description of silica gel and precipitated silica may befound, for example, in the Encyclopedia of Chemical Technology, FourthEdition (1997), Volume 21, Kirk-Othmer in Pages 1020 through 1023.

While silica gels are a form of precipitated silica, this invention isintended to be a significant departure therefrom in a sense of havingthe aforesaid required BET and CTAB surfaces area characterization incombination with the required narrow ratio thereof in a range of from0.8 to 1.3 instead of significantly different precipitated silicas suchas presented in Patent Publication EP 0643015 and mentioned in U.S.Patent Application Publication No. 2008/0293871 as indicated as beinguseful as an abrasive and/or thickening component in toothpaste (ratherthan for suitable rubber reinforcement) with a BET surface area of 10 to130 m²/g and CTAB surface area of 10 to 70 m²/g combined with a BET toCTAB surface area ratio of approximately 1 to 5.2.

Rubber compositions are often prepared by mixing a diene-based rubber,carbon blacks and other rubber compounding ingredients, exclusive ofsulfur based rubber curatives, in at least one sequential mixing stepwith at least one mechanical mixer, usually referred to as“non-productive” mix step, or stage(s), to a an elevated temperatureunder high shear rubber mixing conditions followed by a final mix step,or stage, in which sulfur based curative(s), such as sulfur and sulfurcure accelerators, are added and mixed therewith at a lower mixingtemperature to avoid unnecessarily pre-curing the rubber mixture duringthe mixing stage. The terms “non-productive” and “productive” mix stagesare well known to those having skill in the rubber mixing art.

It is to be appreciated that the rubber composition is conventionallycooled to a temperature below about 40° C. between the aforesaid mixstages.

The sulfur vulcanizable elastomers may be comprised of, for example, atleast one of polymers of at least one of isoprene and 1,3-butadiene andcopolymers of styrene with at least one of isoprene and 1,3-butadiene.

If desired, at least one of the sulfur vulcanizable elastomers may becomprised of:

(A) a coupled elastomer comprised of a polymer of at least one ofisoprene and 1,3-butadiene and copolymer of styrene with at least one ofisoprene and 1,3-butadiene,

wherein said coupled elastomer is at least one of tin and silica coupledelastomer, or

(B) functionalized elastomer of at least one of styrene/butadienecopolymer elastomer (SBR), cis 1,4-polybutadiene elastomer and cis1,4-polyisoprene elastomer;

wherein said functionalized elastomer contains functional group(s)comprised of:

-   -   (1) amine functional group reactive with said allyl        functionalized precipitated silica, or    -   (2) siloxy functional group reactive with said allyl        functionalized precipitated silica filler rubber reinforcement,        or    -   (3) combination of amine and siloxy functional groups reactive        with said allyl functionalized silica, or    -   (4) silane/thiol functional group reactive with said allyl        functionalized silica, or    -   (5) hydroxyl functional groups reactive with said allyl        functionalized precipitated silica, or    -   (6) epoxy groups reactive with said allyl functionalized        precipitated silica, or    -   (7) carboxyl groups reactive with said allyl functionalized        precipitated silica.

The following examples are provided to further illustrate the inventionin which the amounts and percentages of materials are by weight unlessotherwise indicated.

Example I Preparation of Allyl Functionalized Precipitated Silica

Precipitated silica (agglomerated synthetic amorphous silica aggregates)was obtained as Zeosil™ 1165 MP (Micropearl), a product of Rhodia.

The precipitated silica in its agglomerate form was placed in a highspeed blender for 3 minutes to break it (somewhat de-agglomerate it)into a less dense form of precipitated silica aggregates.

The broken up (de-agglomerated) silica aggregates are referred to hereinas Silica A.

(A) Treatment with Allyltrichlorosilane

Thirty grams of the precipitated silica aggregates was placed into around bottomed flask equipped with a Dean-Stark Trap together with drytoluene.

The silica/toluene suspension was heated and refluxed in the flask and awater/toluene mixture containing about 1.65 ml of water was collected(removed from the refluxing suspension) by azeotropic distillation. Thewater/mixture collected (removed) contained about 5.5 percent by weightof the original silica.

To the remaining silica/toluene mixture was added 2.6 gm ofallyltrichlorosilane dropwise to the refluxing suspension in the flask.As the allyltrichlorosilane was added, the suspension became lessviscous and more transparent which indicated that a solution wasforming. The solution was stirred under reflux conditions for two hoursand then cooled and filtered to obtain the treated (allylfunctionalized) precipitated silica.

The collected treated (allyl functionalized) precipitated silica isreferred to herein as Silica B.

(B) Treatment with Allylchlorodimethylsilane

Thirty grams of the precipitated silica aggregates were similarlyprocessed using 1.19 gm of allylchlorodimethylsilane.

The collected treated (allyl functionalized) precipitated silica isreferred to herein as Silica C.

(C) Treatment with Allyltriethoxysilane

Thirty grams of the precipitated silica aggregates were similarlyprocessed using 1.82 gm of allyltriethoxysilane.

The collected treated (allyl functionalized) precipitated silica isreferred to herein as Silica D.

(D) Treatment with N-Propyltriethoxysilane (not an Allylalkoxysilane)

Thirty grams of the precipitated silica aggregates were similarlyprocessed using 1.83 gm of N-propyltriethoxysilane.

The collected treated precipitated silica is referred to herein asSilica E.

Example II Evaluation of Pre-Treated Precipitated Silicas

The treated samples of precipitated silica of Example I were evaluatedin a rubber composition. The following Table A represents the generalrubber formulation. The parts and percentages are by weight unlessotherwise indicated.

TABLE A Parts Non-Productive Mix Stage (NP) Natural cis 1,4-polyisoprenerubber¹ 100 Fatty acid² 1 Coupling agent³ 0 and 4 Carbon black⁴ 4Precipitated silicas⁵ 50 Productive Mix Stage (PR) Sulfur 1.5Sulfenamide sulfur cure accelerator 2 Zinc oxide 1.5 Antioxidant, aminebased 0.5 ¹Natural rubber, SMR20 ²Mixture comprised of stearic, palmiticand oleic acids ³Coupling agent comprised of bis(3-triethoxypropyl)tretrasulfide having an average of from about 3.2 to about 3.8connecting sulfur atoms in its polysulfidic bridge from Evonic Degussaas Si69^(™). ⁴Rubber reinforcing HAF (high abrasion furnace) carbonblack as N330, an ASTM designation. ⁵Precipiated silicas from Example Ias: Silica A, de-agglomerated untreated aggregates of precipitatedsilica as Zeosil ™ 1165 MP having a BET nitrogen surface area of about165 m²/g; a CTAB surface area of about 160 m²/g and therefore with aBET/CTAB ratio of about 1.03. Silica B, an allyltrichlorosilane treatedprecipitated silica Silica C, an allylchlorodimethylsilane treatedprecipitated silica Silica D, an allyltriethoxysilane treatedprecipitated silica Silica E, an N-propyltriethyxysilane treatedprecipitated silica

Samples of the rubber compositions were prepared by blending theingredients in an internal rubber mixer using two separate, sequential,mixing stages, or steps, namely a first non-productive mixing stage (NP)to a relatively high temperature followed by a second, productive mixingstage (PR) to a significantly lower mixing temperature in which thesulfur, sulfur cure accelerator and zinc oxide were added. Such rubbermixing procedure is well known to those having skill in such art.

For the non-productive mixing stage (NP), the ingredients are mixed forabout 4 minutes to an autogeneously generated, via the high shear mixingin the internal rubber mixer, drop temperature of about 150° C. at whichtime the batch is “dropped”, or removed, from the associated internalrubber mixer. The batch is sheeted out and allowed to cool to atemperature below 40° C. The batch is then mixed in a productive mixingstage (PR) during which free sulfur, vulcanization accelerator and zincoxide are added and mixed for a period of about 2 minutes to a droptemperature of about 110° C.

The cure behavior and various cured physical properties of therespective Samples are shown in the following Table 1. For the curedrubber Samples, the Samples were individually cured for about 30 minutesat a temperature of about 150° C.

The rubber samples are identified as Control rubber Sample A andExperimental rubber Samples B, C, D and E.

TABLE 1 Control Sample Experimental Samples A B C D E Materials (phr)Coupling agent 4 0 0 0 0 Silica A - untreated precipitated silica 50 0 00 0 Silica B - allyltrichlorosilane treated silica 0 50 0 0 0 Silica C -allylchlorodimethylsilane treated silica 0 0 50 0 0 Silica D -allyltriethoxysilane treated silica 0 0 0 50 0 Silica E -N-propyltriethoxysilane treated silica 0 0 0 0 50 Test Properties MDR¹,150° C., 60 minutes Maximum torque − Minimum torque (dNm) 17.2 16.1 20.217.7 19.7 ATS², stress-strain (cured 30 min. at 150° C.) 100% ringmodulus (MPa) 1.9 1.1 1.4 1.2 1.1 300% ring modulus (MPa) 9.2 4.7 6 5.14.3 Tensile strength (break strength), (MPa) 23.9 11.1 17.5 34.2 18.3Elongation at break (%) 561 494 546 678 648 Energy to achieve a 300%strain (Joules) 4.1 2.4 3 2.4 2.1 RPA³ (150° C. cure cycle, 11 Hz, 10%strain, 100° C.) Storage modulus (G′), (MPa) 1693 1352 1747 1889 1684Tan delta 0.11 0.22 0.16 0.16 0.17 ¹Rheometer (MDR) instrument²Automated Testing System (ATS) instrument ³Rubber Process Analyzer(RPA) instrument

It can be seen from Table 1 that both the 100 percent and 300 percentmodulus values were higher for rubber Samples B, C and D using the allylsilane treated (allyl functionalized) Silicas B, C and D, respectively,as compared to Experimental rubber Sample E which used the propylsilanetreated Silica E.

The energy to achieve a 300 percent strain is also seen to be higher forthe rubber Samples B, C and D using the allyl silane treated (allylfunctionalized) silicas as compared to rubber Sample E which used thepropyltriethoxysilane (non allyl-containing silane) treated Silica E.The energy to achieve a 300 percent strain is considered to be a measureof the polymer crosslinking, entanglements and polymer/fillerinteraction. Since the cure system and rubber (natural rubber) are thesame for the rubber Samples, then an increase in the energy to achieve a300 percent strain is an indication of increased polymer/fillerinteraction for the allyl silane treated (allyl functionalized)precipitated silicas.

The MDR difference between maximum torque and minimum torque is seen tobe lower for the rubber Samples B and D containing the respective allylsilane treated (allyl functionalized) precipitated Silica B and SilicaD, respectively, as compared to rubber Sample F containing thepropylalkoxysilane treated Silica F.

The MDR difference between maximum torque and minimum torque is seen tobe slightly higher for the rubber Sample C containing the respectiveallyl silane treated (allyl functionalized) precipitated Silica C, ascompared to rubber Sample F containing the propylalkoxysilane treatedSilica F.

It is considered that the higher modulus values taken together withlower or substantially equivalent maximum and minimum torque differencesis further indicative of an increased amount of rubber/fillerinteraction for the rubber Samples B, C, and D containing the allylsilane treated (allyl functionalized) precipitated silicas as comparedto rubber Sample F containing the propylalkoxysilane treated Silica F.

It is concluded herein that the allyl groups on the allyl silane treated(allyl functionalized) precipitated silicas are participating in thesulfur vulcanization process in a manner of creating a coupling bondfrom the precipitated silica to the rubber.

Example III Evaluation of in Situ Treated Precipitated Silica

Precipitated silica (agglomerated synthetic amorphous silica aggregates)was obtained as Zeosil™ 1165 MP (Micropearl), a product of Rhodia.

Rubber samples were prepared by blending an allylalkoxysilane and apropylalkoxysilane (not an allyl silane), separately and individually,with the precipitated silica-containing rubber composition.

In this manner, then, the precipitated silica is treated with theallylalkoxysilane or propylalkoxysilane in situ in the rubbercomposition in an internal rubber mixer.

The rubber samples are referred to herein as rubber Sample X and rubberSample Y.

For rubber Sample X, the allylalkoxysilane was allyltriethoxysilane.

For rubber Sample Y, the propylsilane was N-propyltriethoxysilane.

Samples of the rubber compositions were prepared in the manner ofExample I except for addition of the precipitated silica, andallylalkoxysilane or propylalkoxysilane separately.

The following Table B represents the general rubber formulation. Theparts and percentages are by weight unless otherwise indicated.

TABLE B Parts Non-Productive Mix Stage (NP) Natural cis 1,4-polyisoprenerubber¹ 100 Fatty acid² 1 Coupling agent³ 0 Carbon black⁴ 4 Precipitatedsilica⁶ 50 Allyltriethoxysilane 3.4 N-propyltriethoxysilane 3.5Productive Mix Stage (PR) Sulfur 1.5 Sulfenamide sulfur cure accelerator2 Zinc oxide 1.5 Antioxidant, amine based 0.5 ⁶Precipitated silica asZeosil ™ 1165 MP from Rhodia

The ingredients were those used in Table A of Example II except for theprecipitated silica in its agglomerated form

The cure behavior and various cured physical properties of therespective Samples are shown in the following Table 3. For the curedrubber Samples, the Samples were individually cured for about 30 minutesat a temperature of about 150° C.

TABLE 2 Experimental Rubber Samples F G Materials Allyltriethoxysilanein situ treated precipitated silica 3.4 0 N-propylalkoxysilane in situtreated precipitated silica 0 3.5 Test Properties MDR, 150° C., 60minutes Maximum torque-Minimum torque (dNm) 17.6 17.9 Stress-strain(cured 30 min. at 150° C.) 100% modulus (MPa) 1.5 1.2 300% modulus (MPa)6.9 5.2 Tensile strength (MPa) 19.8 23.2 Elongation at break (%) 575 677Energy to achieve a 300% strain (Joules) 3.3 2.3 RPA (150° C. curecycle, 11 Hz, 10% strain, 100° C.) Storage modulus (G′) 1545 1541 Tandelta 0.15 0.17

It can be seen from Table 2 that both the 100 percent and 300 percentmodulus values were higher for rubber Sample F using theallyalkoxysilane in situ treated silica as compared to rubber Sample Gwhich used the propylalkoxysilane in situ treated silica.

The Energy to achieve a 300 percent strain is seen to be higher for therubber Sample F using the allylalkoxysilane in situ treated silica ascompared to rubber Sample G which used the propylsilane in situ treatedsilica and the difference between MDR maximum and minimum torque valuesare substantially equivalent. The higher energy to achieve a 300 percentstrain together with the substantially equivalent difference betweenmaximum and minimum torque values is indicative of improvedrubber/filler interaction for Sample F as compared to rubber Sample G inwhich the propylalkoxysilane was used to treat the precipitated silicain situ.

The tan delta value is lower for the rubber Sample F in which the silicawas treated in situ with the allylalkoxysilane as compared to the rubberSample G in which the silica was treated in situ with thepropylalkoxysilane. This is indicative of improved rubber/fillerinteraction for the rubber Sample F which is, in turn, indicative oflower internal heat build up for the Sample F rubber composition andbeneficially lower rolling resistance for a vehicular tire having atread of such rubber composition.

It is concluded herein that the allyl groups on the allylalkoxysilane insitu treated precipitated silica are participating in the sulfurvulcanization process in a manner of creating a coupling bond to therubber.

Example IV

Additional treated precipitated silicas were prepared in the manner ofExample I and identified herein as Silica X and Silica Y.

Silica X contained 3 percent allyl groups in its surface prepared bytreating the precipitated silica with allyltriethoxysilane.

Silica Y contained 3 percent propyl groups on its surface prepared bytreating the precipitated silica with propyltriethoxysilane.

Rubber compositions were individually prepared with Silica X and SilicaY, respectively, as well as the untreated silica identified herein asSilica Z.

Silica Z is a precipitated silica comprised ofbis(3-triethoxysilylpropyl)polysulfide having an average in a range offrom about 3.4 to about 3.8 connecting sulfur atoms in its polysulfidicbridge as Si69™ from Evonic Degussa.

The following Table C represents the general rubber formulation. Theparts and percentages are by weight unless otherwise indicated.

TABLE B Parts Non-Productive Mix Stage (NP) Cis 1,4-polybutadienerubber⁷ 0 and 25 Solution polymerization prepared styrene/butadiene 0and 75 rubber (S-SBR)⁸ Natural cis 1,4-polyisoprene rubber¹  0 and 100Naphthenic rubber processing oil 20 Wax (microcrystalline) 1 Fatty acid²2 Coupling agent³  0 and 5.2 Carbon black⁴ 5.2 Silica Z (untreatedprecipitated silica)⁶ 0 and 65 Silica X (Allyltriethoxysilane treatedprecipitated silica) 0 and 69 Silica Y (N-propyltriethoxysilane treatedprecipitated silica) 0 and 69 Productive Mix Stage (PR) Sulfur 1.5Sulfenamide sulfur cure accelerator 1.5 Zinc oxide 1 Antioxidant, aminebased 0.5 Diphenylguanidine secondary sulfur cure accelerator 2 ⁷Cis1,4-polybutadiene rubber as Budene ™ 1207 from The Goodyear Tire &Rubber Company ⁸Solution polymerization prepared SBR as Solflex ™ 33H23from The Goodyear Tire & Rubber Company

Rubber Samples H through M were prepared in the manner of Example I.

The cure behavior and various cured physical properties of therespective Samples are shown in the following Table 3. For the curedrubber Samples, the Samples were individually cured for about 30 minutesat a temperature of about 150° C.

The rubber samples are identified as Control S-SBR rubber Sample H andExperimental S-SBR rubber Samples I and J. The Control Natural Rubber isSample K and the Experimental Natural rubber Samples L and M.

TABLE 3 Control Sample Experimental Samples H I J K L M Materials (phr)Cis 1,4-polybutadiene rubber 25 25 25 0 0 0 S-SBR 75 75 75 0 0 0 Naturalrubber 0 0 0 100 100 100 Coupling agent 5.2 0 0 5.2 0 0 Silica X -allyltrichlorosilane treated silica 0 69 0 0 69 0 Silica Y -propylalkoxysilane treated silica 0 0 69 0 0 69 Silica Z - untreatedprecipitated silica 65 0 0 65 0 65 Test Properties MDR, 150° C., 60minutes Maximum torque less Minimum torque (dNm) 16.2 15.8 11.6 21.918.1 22.72 Scorch time⁴ TS1 (minutes) 0.8 5.7 7.3 0.3 0.7 2.25 Scorchtime⁴ TS2 (minutes) 4 6.2 7.9 0.8 7 2.97 ATS, stress-strain (cured 30min. at 150° C.) 100% ring modulus (MPa) 2.7 2.6 1.2 3.2 2.7 1.33 300%ring modulus (MPa) 10.7 13.7 4.4 14 11.3 4.31 Tensile strength (breakstrength), (MPa) 14.8 21.6 15.5 24.5 23.4 18.59 Elongation at break (%)428 439 581 486 532 612 Energy to achieve a 300% strain (Joules) 5.4 6.22.1 6.8 5.7 2.31 RPA (150° C. cure cycle, 11 Hz, 10% strain, 100° C.)Storage modulus (G′), (MPa) 1619 1654 1208 2172 1975 2171 Tan delta 0.060.07 0.08 0.11 0.12 0.125 ⁴Scorch time is the time in minutes to aspecified torque rise in the Rheometer. For example, in the Table, TS1and TS2 are the times for a 1 and 2 point rise, respectively, in thetorque.

It can be seen from Table 3 that rubber Sample I containing Silica X(the allyltrialkoxysilane treated precipitated silica) has highermodulus values, higher tensile strength and higher energy (at 300percent modulus) than rubber Sample J which contained Silica Y (thepropylalkoxysilane treated precipitated silica). This is indicative ofincreased rubber/filler interaction due to the presence of the allylgroup(s) on the precipitated silica.

It can also be seen from Table 3 that Sample I has higher modulusvalues, higher tensile strength and higher energy to achieve 300 percentstrain than rubber Sample H. This is considered herein to be surprisingsince rubber Sample H uses the silica coupler. This is furtherindicative of increased rubber/filler interaction due to the presence ofthe allyl group(s) on the precipitated silica.

In Table 3, scorch times TS1 and TS2 are reported for rubber Samples Hthrough M. It can be seen that rubber Samples J and M which containedthe propylalkoxysilane treated silica (Silica Y) had the longest scorchtimes which is an indication of the ability to process the rubbercomposition without premature curing, or scorching. This is notconsidered herein to be surprising since the propyl group is notreactive with the elastomer.

It can be seen that rubber Samples I and L which contained the allylsilane treated (allyl functionalized) precipitated silica (Silica X) hadthe next longest scorch times. This is considered herein to be anadvantage since the Silica X has an ability to bond to the elastomer yethave increased processing times (until scorching) as compared to therubber Samples H and K which used conventional coupling with theinclusion of the coupling agent.

DRAWING

A drawing is provided as FIG. 1 (FIG. 1) in order to further illustratethe invention as presented in this Example IV. The drawing is agraphical plot of time in minutes (x-axis) versus torque at a constanttemperature of 150° C. The torque (y-axis) is reported as dNm.

IN THE DRAWING

From FIG. 1 it is seen that for Control rubber Sample H using thenon-treated silica the torque begins to increase immediately. Thisphenomenon is an indication of the reaction between the coupling agentwhich has become bound to the silica and the rubber during the mixing ofthe rubber composition at an elevated temperature.

This immediate rise in torque is considered herein to be unfavorable formanufacturing plant rubber processing because it is indicative of arapid increase in Mooney viscosity of the rubber composition. Theincrease in rubber viscosity is generally unfavorable for processing ofthe rubber composition during its mixing in an internal rubber mixer aswell as its subsequent processing such as by shaping (e.g. by extrusion)and by providing resistance to the flow of the rubber within a rubbermold for shaping and curing the rubber composition such as, for example,in the manufacturing of a rubber tire.

It is seen that for Experimental rubber Sample I the torque remainedstable and did not significantly rise for the first 4 minutes of mixing.This delayed effect in considered herein to be important for reducingthe Mooney viscosity buildup of the rubber composition to therebypromote better and more efficient processing within the internal rubbermixer.

It can also be seen that Experimental rubber Sample I has a faster rateof torque increase after the aforesaid 4 minute period of mixing. Thisis an indication that faster (shorter) rubber molding times are possiblefor manufacturing rubber articles.

Example V

Rubber reinforcing effects of allyl treated precipitated silica andallyl treated silica gel is evaluated.

The precipitated silica is identified herein as Silica P and the allyltreated precipitated silica is identified herein as Silica A-P.

The silica gel is identified herein as Silica G and the allyl treatedsilica gel is identified herein as Silica A-G.

For this Example, the precipitated silica used was Zeosil 1165 MP™ fromRhodia.

For this Example, the silica gel used was SiliaBond™ from the Silicyclecompany.

The following Table D represents the general rubber formulation. Theparts and percentages are by weight unless otherwise indicated.

TABLE D Parts Non-Productive Mix Stage (NP) Cis 1,4-polybutadienerubber⁷ 30 Solution polymerization prepared styrene/butadiene 70 rubber(S-SBR)⁸ Naphthenic rubber processing oil 11 Wax (microcrystalline) 1Fatty acid2 2 Coupling agent3  0 and 5.2 Carbon black4 5.2 Silica Z(untreated precipitated silica)6 0 and 65 Silica A-P (allyl treatedprecipitated silica) 0 and 65 Silica A-G (allyl treated silica gel) 0and 65 Productive Mix Stage (PR) Sulfur 1.5 and 2   Sulfenamide sulfurcure accelerator 1.6 Zinc oxide 1 Antioxidant, amine based 0.5Diphenylguanidine secondary sulfur cure accelerator 0.75 and 1.5   ⁷Cis1,4-polybutadiene rubber as Budene ™ 1207 from The Goodyear Tire &Rubber Company ⁸Solution polymerization prepared SBR as Solflex ™ 16S42from The Goodyear Tire & Rubber Company

Rubber samples N, O, and P were prepared in the manner of Example I. Thecure behavior and physical properties of the respective Samples areshown in the following Table 4. For the cured rubber Samples, theSamples were cured for about 30 minutes at a temperature of about 150°C.

The rubber Samples are identified as Control rubber Sample N (with aprecipitated silica reinforcement), Experimental rubber Sample O (withan allyl treated precipitated silica A-P) and Experimental rubber SampleP (with an allyl treated silica gel A-G).

TABLE 4 Control Experimental Sample Samples N O P Materials (phr) Cis1,4-polybutadiene rubber 30 30 30 S-SBR 70 70 70 Coupling agent 5.2 0 0Silica Z-(precipitated silica) 65 0 0 Silica A-P (allyl treatedprecipitated silica) 0 65 0 Silica A-G (allyl treated silica gel) 0 0 65Test Properties MDR, 150° C., 60 minutes Maximum torque less Minimum17.8 18.2 5.2 torque (dNm) Scorch time TS1 (minutes) 0.6 11.4 10 Scorchtime TS2 (minutes) 4.8 12.2 14.1 ATS, stress-strain (cured 30 min. at150° C.) 100% ring modulus (MPa) 2.5 2.7 0.8 300% ring modulus (MPa) 9.68.8 1.7 Tensile strength (break strength), (MPa) 16.3 15.9 2 Elongationat break (%) 447 475 441 Energy to achieve 300% strain (Joules) 5.0 4.61.1 RPA (150° C. cure cycle, 11 Hz, 10% strain, 100° C.) Storage modulus(G′), (MPa) 1909 1949 670 Tan delta 0.13 0.13 0.30

It can be seen from Table 4 that rubber sample O containing Silica A-P(the allyl treated precipitated silica) had cured rubber stress-strainphysical properties such as tensile strength, modulus and elongation aswell as dynamic physical properties (RPA determined) such as storagemodulus (G′) and tan delta similar to rubber Sample N containingprecipitated silica (which had not been allyl treated) together with atraditional silica coupling agent.

This is particularly significant in a sense that the precipitated silica(non allyl treated precipitated silica) needed the silica coupling agentto achieve cured rubber properties similar to the allyl treatedprecipitated silica without an inclusion of the silica coupling agent.

It is believed that this observation is truly remarkable and asignificant departure from past practice.

Further, such overall rubber properties of rubber Sample N aredramatically and significantly better than the overall rubber propertiesof rubber Sample O (using the allyl treated silica gel), including thesignificantly reduced energy to achieve a 300 percent strain.

This is particularly significant in a sense that it was only the allyltreated precipitated silica (rubber reinforcement quality silica) whichwas observed to also achieve the beneficial cured rubber propertiesinstead of the allyl treated silica gel.

These significant physical differences are considered herein to be aclear indication that the allyl treated precipitated silica (Silica Athrough P) has a significantly greater rubber reinforcing ability thanthe allyl treated silica gel (Silica A through G).

Further, it is seen that treating the silica gel with the allyl silanewas not sufficient to enable the silica gel to become suitable forreinforcement of the rubber.

Accordingly, it is apparent that the silica structure is significant,particularly the combination, for the precipitated silica, of the BETnitrogen surface area, the CTAB surface area and a BET/CTAB ratio in arange of from 0.8 to 1.3.

Accordingly, it is considered herein that a combination of the specifiedprecipitated silica structure and its allyl treatment is a significantaspect of this invention for providing rubber reinforcement.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

1. An allyl functionalized precipitated silica comprised of aprecipitated silica containing at least one allyl group substituent;wherein said allyl functionalized precipitated silica is represented bya general formula (I):

where Z represents the precipitated silica; R² and R³ are the same ordifferent radicals comprised of an alkyl group containing from 1 to 4carbon atoms, a cycloalkyl group, a phenyl group, and alkene groupcontaining from 3 to 18 carbon atoms or cycloalkene radical having from5 to 8 carbon atoms; and R¹ is an allyl hydrogen containing radicalcomprised of at least one of:—CH₂—CH═CH₂,—CH₂—CH═CH—CH₃,—CH₂—CH═C—(CH₃)₂ and—CH₂—C(CH₃)═CH—CH₃ where a is an integer in a range of from 0 to 2, b isan integer in a range of from 0 to 2 and c is an integer in a range offrom 1 to
 3. 2. The allyl functionalized precipitated silica of claim 1wherein said R² and R³ are the same or different radicals comprised ofan alkyl group containing from 1 to 4 carbon atoms.
 3. The allylfunctionalized precipitated silica of claim 1 wherein R¹ is an allylhydrogen containing radical represented as —CH₂—CH═CH₂.
 4. The allylfunctionalized precipitated silica of claim 1 wherein R¹ is an allylhydrogen containing radical represented as —CH₂—CH═CH—CH₃.
 5. The allylfunctionalized precipitated silica of claim 1 wherein R¹ is an allylhydrogen containing radical represented as —CH₂—CH═C—(CH₃)₂.
 6. Theallyl functionalized precipitated silica of claim 1 wherein R¹ is anallyl hydrogen containing radical represented as —CH₂—C(CH₃)═CH—CH₃. 7.An allyl functionalized precipitated silica comprised of a precipitatedsilica treated with at least one allyl silane; wherein said allyl silanehas a general structural formula (II):

where R² and R³ are the same or different and comprised of an alkoxygroup containing from 1 to 8 carbon atoms, a cycloalkoxy groupcontaining from 5 to 8 carbon atoms, an alkyl group containing from 1 to4 carbon atoms, a cyclohexyl group, a phenyl group, an alkene containingfrom 3 to 18 carbon atoms, or a cycloalkene containing 5 to 8 carbonatoms; where X is a chlorine, a hydroxy, or a hydrogen; where R¹ is anallyl hydrogen containing radical comprised of at least one of:—CH₂—CH═CH₂,—CH₂—CH═CH—CH₃,—CH₂—CH═C—(CH₃)₂ and—CH₂—C(CH₃)═CH—CH₃ where a is an integer with a range of from 0 to 3, bis an integer in a range of from 0 to 3, c is an integer in a range offrom 1 to 3, and d is an integer in a range of from 0 to 3 and the sumof a, b, c and d is 4; wherein at least one of X, R² and R³ is present;wherein if d=0, at least one of R² and R³ is an alkoxy group.
 8. Theallyl functionalized precipitated silica of claim 7 wherein said allylsilane is an allylalkoxysilane or allylchlorosilane.
 9. The allylfunctionalized precipitated silica of claim 7 wherein said allyl silaneis comprised of at least one of allyldimethylchlorosilane,allyltrichlorosilane, allylmethyldichlorosilane,diallylchloromethylsilane, diallyldichlorosilane andtriallylchlorosilane.
 10. A method of preparing an allyl functionalizedprecipitated silica which method comprises of treating a precipitatedsilica having hydroxyl groups thereon with at least one allyl silanecompound, wherein said precipitated silica has: (A) a BET nitrogensurface area in a range of from 120 to 300 m²/g, (B) a CTAB surface areain a range of from 100 to 300 m²/g, and (C) a ratio of said BET/CTABsurface areas in a range of from 0.8 to 1.3; wherein said allyl silanecompound has a general structural formula (II):

where R² and R³ are the same or different and comprised of an alkoxygroup containing from 1 to 8 carbon atoms, a cycloalkoxy groupcontaining from 5 to 8 carbon atoms, an alkyl group containing from 1 to4 carbon atoms, a cyclohexyl group, a phenyl group, an alkene containingfrom 3 to 18 carbon atoms, or a cycloalkene containing 5 to 8 carbonatoms; where X is a chlorine, a hydroxy, or a hydrogen; where R¹ is anallyl hydrogen containing radical comprised of at least one of:—CH₂—CH═CH₂,—CH₂—CH═CH—CH₃,—CH₂—CH═C—(CH₃)₂ and—CH₂—C(CH₃)═CH—CH₃ where a is an integer with a range of from 0 to 3, bis an integer in a range of from 0 to 3, c is an integer in a range offrom 1 to 3, and d is an integer in a range of from 0 to 3 and the sumof a, b, c and d is 4; wherein at least one of X, R² and R³ is present;wherein if d=0, at least one of R² and R³ is an alkoxy group.
 11. Themethod of claim 10 wherein said allyl silane comprised of at least oneof allyltriethoxysilane, allyltrimethoxysilane,allyldimethylchlorosilane, allyltrichlorosilane,allylmethyldichlorosilane, diallylchloromethylsilane,diallyldichlorosilane and triallylchlorosilane.
 12. An allylfunctionalized precipitated silica prepared by the method of claim 10.13. A rubber composition comprised of at least one sulfur cured sulfurvulcanizable elastomer containing at least one reinforcing fillercomprised of said allyl functionalized precipitated silica of claim 1.14. The rubber composition of claim 13 wherein said reinforcing fillerincludes at least one of carbon black and said precipitated silicawithout an allyl substituent.
 15. The rubber composition of claim 13which contains a silica coupling agent having a moiety reactive withhydroxyl groups contained on said precipitated silica and anotherdifferent moiety interactive with said sulfur vulcanizable elastomer(s).16. The rubber composition of claim 14 which contains a silica couplingagent having a moiety reactive with hydroxyl groups contained on saidprecipitated silica and another different moiety interactive with saidsulfur vulcanizable elastomer(s).
 17. The rubber composition of claim 13wherein said sulfur vulcanizable elastomer is comprised of at least oneof: (A) polymers of at least one of isoprene and 1,3-butadiene andcopolymers of styrene and at least one of isoprene and 1,3-butadiene,(B) coupled elastomer comprised of a polymer of at least one of isopreneand 1,3-butadiene and copolymer of styrene with at least one of isopreneand 1,3-butadiene, wherein said coupled elastomer is at least one of tinand silica coupled elastomer, and (C) functionalized elastomer of atleast one of styrene/butadiene copolymer elastomer (SBR), cis1,4-polybutadiene elastomer and cis 1,4-polyisoprene elastomer; whereinsaid functionalized elastomer contains functional group(s) comprised of:(1) amine functional group reactive with said allyl functionalizedprecipitated silica, or (2) siloxy functional group reactive with saidallyl functionalized precipitated silica filler rubber reinforcement, or(3) combination of amine and siloxy functional groups reactive with saidallyl functionalized silica, or (4) silane/thiol functional groupreactive with said allyl functionalized silica, or (5) hydroxylfunctional groups reactive with said allyl functionalized precipitatedsilica, or (6) epoxy groups reactive with said allyl functionalizedprecipitated silica, or (7) carboxyl groups reactive with said allylfunctionalized precipitated silica.
 18. The rubber composition of claim13 wherein said precipitated silica is allyl functionalized by: (A)treating said precipitated silica with said allyl silane prior toaddition to said rubber composition, or (B) treating said precipitatedsilica with said allyl silane in situ within the rubber composition. 19.An article of manufacture having at least one component comprised of therubber composition of claim
 13. 20. A tire having at least one componentcomprised of the rubber composition of claim 13.